[Java知识库]设计模式---责任链模式

使多个对象都有机会处理请求，从而避免了请求的发送者和接受者之间的耦合关
系。将这些对象连成一条链，并沿着这条链传递该请求，直到有对象处理它为止

例子1：字符串过滤

//消息类
class Msg {
    String name;
    String msg;

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    @Override
    public String toString() {
        return "Msg{" +
                "msg='" + msg + '\'' +
                '}';
    }
}


//定义过滤器接口
interface Filter {
    boolean doFilter(Msg m);
}


//过滤器实现类1
class HTMLFilter implements Filter {
    @Override
    public boolean doFilter(Msg m) {
        String r = m.getMsg();
        r = r.replace('<', '[');
        r = r.replace('>', ']');
        m.setMsg(r);
        return true;
    }
}

//过滤器实现类2
class SensitiveFilter implements Filter {
    @Override
    public boolean doFilter(Msg m) {
        String r = m.getMsg();
        r = r.replaceAll("996", "955");
        m.setMsg(r);
        return false;
    }
}

//过滤器实现类3
class FaceFilter implements Filter {
    @Override
    public boolean doFilter(Msg m) {
        String r = m.getMsg();
        r = r.replace(":)", "^V^");
        m.setMsg(r);
        return true;
    }
}

//过滤器实现类4
class URLFilter implements Filter {
    @Override
    public boolean doFilter(Msg m) {
        String r = m.getMsg();
        r = r.replace("mashibing.com", "http://www.mashibing.com");
        m.setMsg(r);
        return true;
    }
}

//过滤器链
class FilterChain implements Filter {
    private List<Filter> filters = new ArrayList<>();

    public FilterChain add(Filter f) {
        filters.add(f);
        return this;
    }

    public boolean doFilter(Msg m) {
        for(Filter f : filters) {
            if(!f.doFilter(m)) return false;
        }

        return true;
    }
}


//主方法调用
public class Main {
    public static void main(String[] args) {
        Msg msg = new Msg();
        msg.setMsg("大家好:)，<script>，欢迎访问 mashibing.com ，大家都是996 ");

        FilterChain fc = new FilterChain();
        fc.add(new HTMLFilter())
                .add(new SensitiveFilter());

        FilterChain fc2 = new FilterChain();
        fc2.add(new FaceFilter()).add(new URLFilter());

        fc.add(fc2);

        fc.doFilter(msg);
        System.out.println(msg);

    }
}

例子2：java中sevrlet过滤器

request 经过过滤器 1--->2,response 经过过滤器2--->1

//request
class Request {
    String str;
}

//response
class Response {
    String str;
}


//过滤器接口
interface Filter {
    void doFilter(Request request, Response response, FilterChain chain);
}

//过滤器实现类1
class HTMLFilter implements Filter {
    @Override
    public void doFilter(Request request, Response response, FilterChain chain) {
        request.str = request.str.replaceAll("<", "[").replaceAll(">", "]") + "HTMLFilter()";
        chain.doFilter(request, response);
        response.str += "--HTMLFilter()";

    }
}

//过滤器实现类2
class SensitiveFilter implements Filter {
    @Override
    public void doFilter(Request request, Response response, FilterChain chain) {
        request.str = request.str.replaceAll("996", "955") + " SensitiveFilter()";
        chain.doFilter(request, response);
        response.str += "--SensitiveFilter()";

    }
}

//过滤器链
class FilterChain {
    List<Filter> filters = new ArrayList<>();
    int index = 0;

    public FilterChain add(Filter f) {
        filters.add(f);
        return this;
    }

    public void doFilter(Request request, Response response) {
        if(index == filters.size()) return;
        Filter f = filters.get(index);
        index ++;

        f.doFilter(request, response, this);
    }
}


//主程序
public class Servlet_Main {
    public static void main(String[] args) {
        Request request = new Request();
        request.str = "大家好:)，<script>，欢迎访问 mashibing.com ，大家都是996 ";
        Response response = new Response();
        response.str = "response";

        FilterChain chain = new FilterChain();
        chain.add(new HTMLFilter()).add(new SensitiveFilter());
        chain.doFilter(request, response);
        System.out.println(request.str);
        System.out.println(response.str);

    }
}